In recent year, development efforts are directed to four wheel steering vehicles equipped with a rear wheel toe angle control system for variably controlling the rear wheel toe angles with the aim of improving the yaw response of the vehicle and the driving stability of the vehicle. In a known rear wheel toe angle control system, an electric actuator is provided in a connecting part between a lateral link or a trailing link of each rear wheel suspension system and the vehicle body such that the toe angles of the rear wheels can be individually varied by appropriately driving the electric actuators. See Patent Document 1, for instance.
The electric actuator typically consists of a linear actuator including an electric motor and a feed screw mechanism. The applicant of this application previously proposed an invention for preventing the dislodging of the output rod without increasing the size of the linear actuator. See Patent Document 2. When the toe angle of each rear wheel is varied by using such an electric actuator, it is a common practice to perform a feedback control by detecting the output (displacement) of the electric actuator, and comparing the actually measured output of the electric actuator with a target output corresponding to a target rear wheel toe angle.